package/kismet: link with libatomic if needed

Fix build of kismet-2020-09-R3 with riscv64

Fixes:
 - http://autobuild.buildroot.org/results/9c3d56ef837c7c5bfbb34a0ec51b349108e201b1

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/kismet/kismet.mk

@@ -27,6 +27,10 @@ endif
 
 KISMET_CONF_ENV += CXXFLAGS="$(KISMET_CXXFLAGS)"
 
+ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
+KISMET_CONF_ENV += LIBS=-latomic
+endif
+
 ifeq ($(BR2_PACKAGE_LIBCAP),y)
 KISMET_DEPENDENCIES += libcap
 KISMET_CONF_OPTS += --enable-libcap